Case-based reasoning (CBR) classifiers use a database of problem solutions to solve new problems. Unlike nearest-neighbor classifiers, which store training tuples as points in Euclidean space, CBR stores the tuples or “cases” for problem solving as complex symbolic descriptions.

1. Case Based Reasoning
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2. Faced this situation before?
• Oops the car stopped.
– What could have gone wrong?
• Aah.. Last time it happened, there was no petrol.
– Is there petrol?
• Yes.
– Oh but wait I remember the tyre was punctured (ban
bocor)
• This is the normal thought process of a human
when faced with a problem which is similar to a
problem he/she had faced before.
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3. So what?
• Reuse the solution experience when faced
with a similar problem.
• This is Case Based Reasoning (CBR)!
– memory-based problem-solving
– re-using past experiences
• Experts often find it easier to relate stories
about past cases than to formulate rules
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4. What’s CBR?
• To solve a new problem by remembering a previous
similar situation and by reusing information and
knowledge of that situation
• Ex: Medicine
– doctor remembers previous patients especially for rare
combinations of symptoms
• Ex: Law
– English/US law depends on precedence
– case histories are consulted
• Ex: Management
– decisions are often based on past rulings
• Ex: Financial
– performance is predicted by past results
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5. CBR Cycle
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6. R4 Cycle
REUSE
propose solutions
from retrieved cases
REVISE
adapt and repair
proposed solution
CBR
RETAIN
integrate in
case-base
RETRIEVE
find similar
problems
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7. CBR System Components
• Case-base
– database of previous cases (experience)
• Retrieval of relevant cases
– index for cases in library
– matching most similar case(s)
– retrieving the solution(s) from these case(s)
• Adaptation of solution
– alter the retrieved solution(s) to reflect differences
between new case and retrieved case(s)
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8. Two big tasks of CBR
• Classification tasks (good for CBR)
– Diagnosis - what type of fault is this?
– Prediction / estimation - what happened when
we saw this pattern before?
• Synthesis tasks (harder for CBR)
– Engineering Design
– Planning
– Scheduling
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9. Technical
Diagnosis of
Car Faults
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10. Problem to be solved
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11. How CBR solves problems
• New problem can be solved by
– retrieving similar problems
– adapting retrieved solutions
• Similar problems have similar solutions
?
S
SS
S
S
S
S
S
S
P
P
PPPP
P
P
P
X
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12. New Car Diagnosis Problem
• A new problem is a case without a
solution part
• Not all problem features must be
known
– same for cases
– Problem
• Symptom: brake light does not work
• Car: Ford Fiesta
• Year: 1997
• Battery: 9.2v
• Headlights: undamaged
• Headlight Switch: ?
Feature Value
New
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13. • Compare new problem to each case
• Select most similar
• Similarity is most important concept in CBR
– When are two cases similar?
– How are cases ranked according to similarity?
• Similarity of cases
– Similarity for each feature
• Depends on feature values
Retrieving A Car Diagnosis
Case
New Problem
CaseCaseCaseCaseCaseCaseCaseCase1
Similar?
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14. Similarity Computation for case 1
Figure Credit: R. Bergmann, University of Kaiserslautern
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15. Similarity Computation for case 2
Figure Credit: R. Bergmann, University of Kaiserslautern
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16. Similarity Measurement
• Purpose: To select the most relevant case
• Basic Assumption: Similar problems have similar
solutions
• Similarity value between 0 and 1 are assigned
for feature value pairs
• E.g.: Feature: Problem
Front Light does not work
Break Light does not work
.8
Front Light does not work
Engine doesn’t start
.4
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17. Similarity Measurement
• Feature: Battery Voltage
• Different features have different
importance
• Two kinds of Similarity Measures
– Local Similarity – similarity on feature level
– Global Similarity - similarity on case or object
level
12.6 13.6 12.6 6.7.9 .1
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18. Reuse Solution from Case 1
New Problem
• Symptom: brakelight does not work
• Car: Ford Fiesta
• Year: 1997
• Battery: 9.2v
• Headlights: undamaged
• HeadlightSwitch: ?
Problem
• Symptom: headlight does not work
• …
Solution
• Diagnosis: headlight fuse blown
• Repair: replace headlight fuse
– Solution to New Problem
• Diagnosis: headlight fuse blown
• Repair: replace headlight fuse
– After Adaptation
• Diagnosis: brakelight fuse blown
• Repair: replace brakelight fuse
Case 1
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19. Pros & Cons of CBR
• Advantages
– solutions are quickly proposed
• derivation from scratch is avoided
– domains do not need to be completely understood
– cases useful for open-ended/ill-defined concepts
– highlights important features
• Disadvantages
– old cases may be poor
– library may be biased
– most appropriate cases may not be retrieved
– retrieval/adaptation knowledge still needed
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20. CBR Resources
• Books
– I. Watson. Applying Knowledge Management: Techniques For
Building Corporate Memories. Morgan Kaufmann, 2003.
– I. Watson. Applying Case-Based Reasoning: Techniques for
Enterprise Systems. Morgan Kaufmann, 1997.
• CBR on the web
– http://groups.yahoo.com/group/case-based-reasoning/
• CBR Commercial Solutions
– Orenge from www.empolis.com
– Kaidara Adviser from (www.kaidara.com)
– eGain (www.egain.com)
• Customer Service & Contact Centre Software
• CBR Tools in our School
– CBR-Works from www.empolis.com
– ReCall from www.isoft.fr
– Weka from www.cs.waikato.ac.nzMohammad Amawi 20